Primary cell



May 27, 1958 c. K. MoREHoUsE Erm. 2,836,645

PRIMARY CELL Filed June 13. 1956 INVENTOR.

also/MM; 7/Mf (buf/fs) E SN H E um y M m M KD M am HT Em H R m Y B.

United States Patent O PRIMARY Cntr.

Clarence K. Morehouse, Princeton, and Richard Giicksman, Highland Park,N. Ii., assigner-rs to Radio Corporation of America, a corporation ofBelau/are Application .lune 13, 1956, Serial No. %,241

Claims. (Cl. 136-137) This invention relates to primary cells, andparticular- 1y, but not necessarily exclusively, to improved primarycells including a magnesium anode and a cathode comprising a quinoneorganic compound.

Primary cells are electrochemical devices from which stored chemicalenergy is converted directly into electrical energy by anelectrochemical process. Generally, the term primary cells refers to aclass of cells that do not have efficiently reversible chemicalreactions. Once the chemical energy is converted to electrical energy,the cells are discarded. Primary cells that are manufactured to includea non-spillable electrolyte are referred to as dry cells. Primary cellsthat are assembled without one of the essential components, such as theelectrolyte, but are adapted to supply electrical energy when thecomponent is added just prior to use, are referred to as reserve cells.

A primary cell which is to be used as a portable power supply shouldhave the following characteristics: a high watt-hour and a highampere-hour capacity per unit of volume or weight; a high flat operatingvoltage over a Wire range of current drains; a long life; and a lowcost.

One problem in present day primary cells is that they include materialswhich come into short supply in times of emergency because the materialsbecome critical to the interests of the United States as a whole. Thesematerials may become critical because they are supplied from foreignsources or because domestic ore sources are limited in size and miningcapacity, or for some other economic reason.

Accordingly, an object of this invention is to provide primary cellswhich are comparatively inexpensive to manufacture, have a highwatt-hour and a high amperehour capacity per unit of volume or Weight,and have a relatively high at operating voltage level over a wide rangeof current drains. Y

A further object is to provide an improved electrochemical system whichmay be employed for primary cells.

Another object is to provide improved primary cells including materialswhich are non-strategic, can be readily available in large quantities inthe United States, and are comparatively inexpensive.

In general, the foregoing objects are accomplished in improved primarycells of the invention which include an anode selected from the groupconsisting of magnesium and magnesium base alloys and a cathodeincluding an organic oxidizing substance in which the oxidizingproperties are due at least in part to the presence of a quinoidstructure in said substance. The invention includes reserve cellscomprising the foregoing combination and adapted to supply electricalenergy upon the addition of an electrolyte.

The invention is described in greater detail by reference to the drawingwherein:

Figure 1 is a sectional, elevational View of a typical dry cell of theinvention, and

Figure 2 is a family of curves showing the change in lil paper.

ICC

cell voltage with respect to discharge time of an AA size dry cell ofthe invention compared with comparable dry cells from otherelectrochemical systems when discharged continuously through a 50 ohmresistance.

Example l.-referring to Figure 1, a dry cell 10 according to theinvention may be prepared as follows. A metallic anode 12 is provided inthe form of a cup of the standard AA size (American StandardsAssociation, Bureau of Standards, Washington, D. C.). The anode 12 hasthe approximate composition 98.4% magnesium, 1.0% aluminum, 0.5% zincand 0.1% calcium. This alloy is sometimes designated AZlOA. The anode 12is lined with a separator 14 comprising an absorbent kraft The separator14 keeps the anode 12 and a cathode 16 apart while providingtherebetween a low resistance path to the iiow of ions during theelectrochemical process.

A rnix including the cathode material and electrolyte, hereinafterreferred to as the cathode mix, is prepared of the followingconstituents:

24 grams p-quinonedioxime 12 grams acetylene black 1 gram bariumchromate 25 ml. an aqueous solution containing 500 grams of MgBr2-6H2Oand l gram Li2CrO4-2H2O per liter of water Approximately 5 grams of thecathode mix is formed to a cylindrical slug and inserted into the paperlined anode 12 to form a cathode 16. A carbon rod 1S is inserted intothe mix l5 to provide electrical connection thereto. The anode 12 issealed by an insulating washer 20 mounted on the carbon rod and a layer22 of hard wax on the washer. A metal Contact cap 24 of brass is placedon rod 18. An air space 26 is provided between the Washer 20 and thecathode 16.

The anode 12 and cathode 16 may now be connected through an externalload whereby the cell commences to be discharged by electrochemicalaction. The cell reactions are believed to occur as follows:

l Cathode reactionV NOH Overall reaction NOH NOH

" quinonedioxime as the cathode material and a magnesium 3- anode(magnesium/p-quinonedioxime). Curve 33 shows the discharge curve for asimilar zinc/p-quinonedioxime cell discharged under the same conditions.For comparison, curve 35 shows the characteristic discharge curve for asimilar. commercially-available zinc/manganese dioxide dry celldischarged under the same conditions. The dry cell of Example 1 exhibitsa atter voltage curve than prior cells resulting inmoreuniformperformance of the equipment which is supplied with electricpower. Also, the dry cell of Example 1 supplies electric power for alonger period of time to a 0.9 volt cuto. This cutoff voltagerepresentsv the practical voltage below which portable electronicequipment ordinarily becomes inoperative.

In addition to its favorable performance, the cell of Example 1 has thegreat advantage Vthat it employs non-strategic, plentiful materialswhich are relatively easy to manufacture in the United States, and whenmanufactured in large quantities, should be relatively inexpen' sive.Magnesium may beobtained from sea Waterand the p-quinonedioxime may beproduced synthetically.

The primary cells of the invention comprise generally the followingparts:

(1) An anode selected from the 'group` of materials consisting ofmagnesium and magnesium-base alloys, (2) An electrolytewhich may include(a) a soluble substance for increasing the electrical-conductivitythereof and (b) a material for inhibiting'the corrosion of the anode, Y

(3) YA cathode including a depolarizr consisting of an organic oxidizingsubstance in which `the oxidizing properties thereof are due at least inpart to the presence of a quinoid structure in said substance.VThevcathode may include also an inorganic depolarizer, otherrorganicdepolarizers and/ or an inorganic material for increasing theconductivity of the cathode. y Y. I

The anode- The anode for the primary cellsV ofthe invention maybe'magnesium or magnesium-base. alloys. The term magnesium anodeincludes both magnesium and magnesium base'alloy anodes. Amagnesium-base alloy is one wherein the predominant ingredient isinaginesium. Thus, any alloy having morethan 50% magnesium issatisfactory. It is preferred,'howeve'r, to have as high` a proportion'iof magnesium as possible;v Other ingredients are added to magnesium toimprove the'oproperties of the anode for fabrication purposes, to imparta greater degree. ofl corrosion resistance, or for other reasons. TableI'set'sY forth examples of magnesium-base alloys which are suitable foranode material together with the corresponding ASTM designations. V

TABLE I Anode compositions A. s. T. M.

Nominal Composition 1 Designa- .Alloy No.

Y tion occ K1 Balance commercial*magnesium.r

The magnesium anode may be the container for the cell, may be the liningof the container, or may be a separate structure inserted in thecontainer. The magnesiurn anode may be in any geometrical configurationdesired.

it is necessary to space the cathode and anode froml one another. Toaccomplish this, it is preferred to insert a separator between the anodeand the cathode regardless of configuration, although other methods ofspacing may be used. The separator may be any porous material such askraft paper, kraft paper treated with agel-like material such ascarboxymethyl cellulose, polyvinyl alcohol, or a starch-flour gel. Thecoating on the kraft paper promotes adhesion of the paper Ytothe anodeand maintains good electrical contacts between the electrolyte and theanode. Porous ceramics or other inorganic or organic structures may beused in place of paper.

The electrolyte-The electrolyte may be an aqueous solution containing`a`soluble salt such as sea water, o1'V water to which one or moresoluble salts have been deliberately added. Bromides of alkali metals,alkaline earth metals, and ammonium cationsV are the most desirablesoluble salts in the electrolyte. The electrolyte may be'prepared bydissolving the salt in water in a concentration between about 30 Vgramsper liter and that producing a saturated ksolution at ordinarytemperatures. A

The concentration does not lappear to be critical, although for bestresults'certain concentrations are to be preferred depending upon theparticular salt or combination of salts It -is also desirable to includein thel electrolyte-orneofrV more alkali metal, alkaline earth -metal(includingmagnesium), or ammonium salts of chromic acid incorrosioninhibitinglamounts. The chromic acid salts'may'he used in:proportions between 0.01 gramper liter Vof solution to concentrationsproducing saturation in the presence of the electrolyte salt obtainedtherein, Y A Vpreferred concentration of lithium chromate is about Y0,05to'ZHgramsv perliter ofgsolution. Examples of corrosion-inhibiting saltsare sodium chromate, lammcniiurn chromate,k potassiun dichromate,lithium dichromate, magnesium chromate, calcium chromate. l y

For certain applications, principally wherea long shelf life isrequired, it is desirable to omit one ofthe essential components utilthe need for electricalenergy has arisen. Theprimary cells of theinvention are particularly adaptable to be lprepared as reserve Vcells,.-for .exampleyby omitting Ythe electrolyte until just prior touse.

Y The cathode-The cathodeiincludes an organic oxidirzing substance, inwhich they oxidizing propertiesgare duejY atleast in'partto the`presence of a quinoid structureV insaid substance. 'These substancesare also referred lto as .quinoneorganic compounds. During theelectrochemical 'action, the substance undergoesa reduction as theprimary cell furnishes electric current. The quinone or-YV ganiccompounds which are insoluble in conventional electrolytes areparticularly suitable for use as cathode materials in dry cells. Quinoneorganic compounds soluble` in the cellelectrolyte may be'used in reservecells.

The following list includes sometofthe quinone orf ganic compounds whichare useful in preparing primary,-

While a single Para-benzoquinone and its derivatives:

p-benzoquinone 2,5 dichloro-p-quinone 2,6 dichloro-p-quinone quinhydronep-toluquinone tetrachloro-p-benzoquinone 2-chlorop-quinone2-phenyl-1,4-benzoquinone sodium nitranilate Ortho-benzoquinone and itsderivatives:

o-benzoquinone tetrachloro-o-benzoquinone tetrabromo-o-benzoquinoneDiphenoquinone and its derivatives:

diphenoquinone 2-chlorodiphenoquinone Alpha and beta naphthoquinones andtheir derivatives:

1,4 naphthoquinone 1,2 naphthoquinone 4 methylox -l,2naphthoquiuone 2methyloxy-1,4-naphthoquinone 3-nitro-l,2naphthoquinone silver salt of2-hydroxy-l,4 naphthoquinone Antllaquinone and its derivatives:

anthraquinone L8 dihydroxyanthraquinone 1,4dihydroxy-2-anthraquinonesulfonic acid 5-nitro-l-anthraquinonesulfonicacid Phenanthrenequinone and its derivatives:

phenanthrenequinone 2-nitrophenanthrenequinone Para-quinoneimine and itsderivatives:

p-quinoneimine N,2,6 trichlorop-quinoneimine N-chloro-p-quinoneiminep-quinonemonoanii Para-quinonediimine and its derivatives;

p-quinonediimine N,N dichloroquinonediimine phenylene blueQuinonemonooxime and its derivatives:

p-quinonemonooxime Quinonedioxirne and its derivatives:

p-quinonedioxime Any quinone organic compound may be used in thecathodes of the primary cells of the invention. The primary cells of theinvention all utilize the electron change obtained in converting aquinoid compound to a benzenoid compound by a structural rearrangement.This is shown schematically by the following equation:

In addition, such compounds may have other radicals in their structurewhich alter their physical and chemical properties to affect thestability and solubility in the electrolyte. It is also recognized thatby changing the structure of the quinone organic compounds, thetheoretical capacity, shelf life and the rate at which electric energycan be withdrawn from the cell can be altered. rhe selection of theparticular compound and its structure will depend on the application forwhich the particular primary cell is intended.

Substituent groups often exert a marked iniiuence on theoxidation-reduction potential in either a positive or negative sense.Meta-directing groups, such as -NO2, -CN -SO2Ar, COAL -COOi-i, -Cl, and--SO3H, raise the potential of the parent quinone, whereas a potentiallowering elfect is exerted by the following groups, arrangedapproximately in order of decreasing eectiveness: NER NH2 -N(CH3)2,-Ol-I, -OR, -CH3, -NHCOCH3, -C6.TI5, -OCOCH3- The relationships arethose expected from the course of aromatic substitutions. Stronglyunsaturated groups and halogen atoms are electron-attracting and tend toincrease the attractive power of the system terminating in the oxygenatoms for external electrons, the acquisition of which converts thequinone into hydroquinone. Amino, hydroxyl, alkyl, and otherelectron-repelling substituents decrease amnity for electrons and hencelower the potential.

"the cathodes of the primary cells of the invention may also comprise amixture of one or more quinone orgamc compounds, or a mixture with oneor more other organic oxidizing compounds, such as nitro orvaniccompounds, or a mixture with inorganic cathode materials such asmanganese dioxide or the like.

For many situations, it is desirable to increase the electricalconductivty of the cathode. One may add varying proportions ofnon-reactive conductive materials to obtain the desired electricalconductivity. Carbon is a preferred material for this purpose because ofits low cost and easy availability. Any of the various forms of carbon,such as graphite, or acetylene black may be used. The conductingmaterial may comprise up to by weight of the cathode mix.

The cathodes of the invention may be fabricated by a number of methodsand in various shapes. Example l describes preparing a mixture ofpowders with electrolyte and then pressing a quantity of the mixture tothe desired shape and density. Another cathode mix may include a bindersuch as polyvinyl alcohol, carboxymethyl cellulose, methylcellulose, avinyl resin, bentonite or silica gel. Such mix may be pressed asdescribed above, or cast in a mold to fabricate the cathode. The binderadds strength and rigidity to the cathode especially where odd shapesare used. A cathode mix containing a binder may be coated on a suitablesupport such as a carbon rod or block and used in layer form. Besidessimple coatings, hns containing the cathode mix may also be prepared bythe addition of a film-forming material to the cathode mix and usingtechniques well-known in the plastics art. One technique is to coatpaper separator sheets with magnesium powder in a binder on one surfaceand the cathode mix in a binder on the other surface. The coated sheetsmay then be stacked stamped to produce batteries of the desired voltageand geometry.

In some cases, it is desirable to increase the amount of active surfaceon the cathode. One method for increas- 'ing the active surface is toadd a propoltion of a soluble material, such as sodium chloride, to thecathode mix before fabrication. Upon fabrication, the soluble materialis dissolved out of the cathode leaving a somewhat porous structure witha greatly increased proportion of active surface.

The presence of atmospheric oxygen enhances the capacity of the cathodesof cells of various kinds. For example, capacity increases can berealized in the cell of Example l by providing a small vent (e. g. 0.05in diameter) in the Wax layer Z2, or by preparing a tab on the washer2t) which tab extends up through the wax layer 22. The maximum effect isordinarily obtained when the drain is relatively light.

It is noteworthy that the materials used to fabricate the cells of theinvention may all be produced in the United States by processes Wellknown in the chemical arts. Magnesium may be produced from sea Waterwhich is in abundant supply in the United States. The quinone organiccompounds may be produced synthetically and many such substances such asp-quinonedioxime, are commercially available at the present nme.Graphite and acetylene black are also available from sources within theUnited States.

Example 2.--Another dry cell according to the inventio'n may be preparedaccording to Example 1 except that thecathode mix has the followingformulation:

16.3 grams N,2,6-t1ichloro-p-quinoneimine 8.15 grams acetylene black 0.9gram BaCrOi 25 ml. of an aqueous solution containing 500 grams ofMgBr26H2O and 1.0 gram Na2Cr2O7-2H2O per liter of water Example3.-Another dry cell according to the invention may be prepared accordingto Example 1 except that the cathode mix has the following formulation:

20 grams 2,5 dichloroquinone 2.5 grams acetylene black v 11 ml. of anaqueous solution containing 500 grams of MgBr26H2O and 1.0 gramLi2CrO4-2H2O per liter of water Example 4.-Another dry cell according tothe invention may be prepared according to Example 1 except that thecathode mix has the following formulation:

20 grams ortho-benzoquinone grams acetylene black 0.9 gram BaCrOi,

21 ml. of an aqueous solution containing 500 Vgrams of MgBr2-6H2O and1.0 gram Li2CrO4-2H2O per liter of water Example 5.-Another dry cellaccording to the invention may be prepared according to Example l exceptthat the cathode mix has the following formulation:

25 grams 2-nitro-1,2-naphthoquinone 12.5 grams acetylene black 0.8 gramBaCrO4 26 ml. of an aqueous solution containing 500 grams of MgBr2-6H2Oand 1.0 gram'LigCrO'ZI-IZO per liter of water Example 15.-Another drycell according to the invention may be prepared according to Example 1except that the cathode mix has the following formulation:

20 grams diphenoquinone 20 grams manganese dioxide grams lacetyleneblack c 45 ml. of an aqueous solution containing 500 grams of MgBr2'6H2Oand 1.0 gram Li2CrO4'2H2O per'liter of water Y Example 7.-Another dry`cell according to the invention may be prepared according to Example 1except that the cathode mix has the following formulation:

grams 2-chloro-p-quinone 20 grams meta-dinitrobenzene grams Darco G-60carbon black 10 grams acetylene black K 93 ml. of an aqueous solutioncontaining 500 gramsof MgBr2-6H2O and 1.0 gram Li2CrO4 per liter ofwater Example 8.-A iiat reserve cell may be prepared by Ist mixing thefollowing formulation:

10 grams N,N dichloro-p-quinonediimine y 5 grams acetylene black 26 inl.solution containing 5% by weight of collodion in ether n Paste aquantity of the cathode formulation to a graphite plate about 1.25" x1.00" x 0.0625 thick and weighing about 2.0 grams. The cathode assemblyis dried, wrapped with a piece of salt-free kraft paper, and thenwrapped with` a piece of magnesium sheet about 3.0 `1.0 x 0.010 thickand weighing about 1.0 gram. When it is desired to use the cell, theentire assembly is immersed in an aqueous solution containing 500 gramsMgBrz-6H2O and 1.0 gram Li2CrO42H2O per kliter of water.

There khave been described improved-primary cells whichare inexpensiveto manufacture and exhibit a high watt-hour and ampere-hour capacity perunit of volume or weight and a high flat operating voltage level over awide range of current drains. The cells ofthe invention use 8 materialswhich may be produced within the United States in large quantities bytechniques well known in the chemical art. i f

What is claimed is:

1. In a primary cell, an anode selectedfrom the group consisting ofmagnesiumand magnesium base alloys, in combination with a cathodeincluding a depolarizer consisting of an organicV oxidizing substance inwhich the oxidizing properties ofsaid substance are ,due at least inpart to the presence of a quinoid structure in said substance.

2. A primary cell according to claim 1 wherein said anode comprines amagnesium base alloy.

3. A primary cell according Ito claim 1 wherein said Vcathode comprisesa mixture of different organic oxidizing substances in which theoxidizing properties of at least one of said substances are due at leastin part to the presence of a quinoid structure in said substances.

4. A primary cell according `to claim 1 wherein said cathode includes aninorganic depolarizer. Y

5. A primary cell according to claim 1 wherein'said cathode includes aninorganic material for increasing the electrical conductivity of saidcathode.

6. A primary cell comprising a magnesium anode, an electrolyte, and acathode including a depolar-izer consisting of an organic oxidizingsubstance in which the oxidizing properties are due at least in part tothe presence of a quinoid structure in said substance.

7. A primary cell according to claim 6 wherein said electrolyte is anaqueous solution having dissolved therein a substance selected from thegroup consisting of alkali metal bromides, alkaline earth metalbromides, and ammonium bromides. A

8. A primary cell according to claimo wherein said electrolyte is anaqueous solution having dissolved therein a chromic acid salt of ananion selected from the group consisting of alkali bases, alkaline earthmetal bases and ammonium bases.

9. A primary cell comprising a magnesium base alloy anode, an aqueouselectrolyte having dissolved ytherein magnesium bromide and a chromateinhibitor, and a cathode comprising carbon and an organic oxidizingsubstance in which the oxidizing properties are due at least in part tothe presence of a quinoid structure in said substance.

10. A primary cell including aV magnesium anode, an aqueous electrolyte,and a cathode including p-quinonedioxime.

11. A primary cell including a magnesium anode,ran aqueous electrolyte,and a cathode including N,Ny dichloro-p-quinonediimine.

12. A primary cell including a magnesium anode, an aqueous electrolyte,and a cathode including diphenoquinone. Y

13. A primary cell including a magnesium anode, an aqueous electrolyte,and a cathode including pquinonedi imine.

14. A primary cell including a magnesium anode, an aqueous electrolyte,and a cathode including sodium nitranilate. f

15. A reserve cell adapted to be used upon the addition of anelectrolyte, said cell comprising a magnesium anode and, associatedtherewith, a cathode comprising a depolarizer consisting of an organicoxidizing substance in which the oxidizing properties are due at leastin part to the presence of a quinoid structure in said substance;

References Cited in the ile of this patent UNITED STATES PATENTS BlakeSept. 30, 1952 OTHER REFERENCES i

1. IN A PRIMARY CELL, AN ANODE SELECTED FROM THE GROUP CONSISTING OFMAGNESIUM AND MAGNESIUM BASE ALLOYS, IN COMBINATION WITH A CATHODEINCLUDING A DEPOLARIZER CONSISTING OF AN ORGANIC OXIDIZING SUBSTANCE INWHICH THE OXIDIZING PROPERTIES OF SAID SUBSTANCE ARE DUE AT LEAST INPART TO THE PRESENCE OF A QUINOID STRUCTURE IN SAID SUBSTANCE.